Process of recovering halogens



Reissued Oct. 15, 1935 UNITED STATES PATENT OFFICE to General SaltCompany,

Ltd., Los Angeles,

Calif., a corporation of California.

No Drawing. Original No. 1,972,546, dated September 4, 1934, Serial No.669,795, May 6, 19$. Application for reissue August 12, 1935, Serial 20Claims. (Cl. 23-217) This invention relates to the recovery of halogens,and particularly to processes for the recovery of iodine or otherhalogen from oil-field brines or other solutions containing the same, inwhich the solution is first treated, if necessary, to convert thehalogen to the form of free or elemental halogen, after which thehalogen is adsorbed on charcoal or other suitable adsorbent agent and isthen converted by suitable chemical treatment into soluble salts orcompounds which are dissolved from the adsorbent agent and recovered byfurther treatment of the resultant liquor. The invention is particularlydirected to the treatment of brines or other solutions containing ahalogen in the presence of organic impurities. The presence of suchimpurities has been found to be quite disadvantageous in the commercialoperation of such processes, since these impurities are largely adsorbedin the adsorbent agent, along with the halogen, and are subsequentlyremoved therefrom with the halogen, resulting in the production of animpure halogen product, a reduction in the yield obtainable, and incertain operating difficulties.

It has been hitherto proposed to partially overcome these disadvantagesby the removal of such impurities through suitable purification treatment, such treatment being applied either to the brine or solution priorto the adsorption step, or to the halogen-containing liquor obtained bychemical treatment and leaching of the halogencontaining adsorbentagent. Such purification methods, however, have not only added anadditional step or steps to the process but have failed to effect acomplete removal of the above described impurities so that, at best onlya partial elimination of the above-mentioned disadvantageous processcharacteristics has been obtained.

The principal object of this invention is to provide a new andadvantageous method of removing or eliminating organic or volatileimpurities present in such a process, and to also provide an improvedmethod of halogen recovery involving such a method of elimination ofimpurities.

A particular object of the invention is to obtain a substantiallycomplete elimination of such impurities, prior to the leaching orsolution of the halogen compounds or salts from the adsorbent agent, soas to entirely eliminate the presence of these impurities in thesucceeding steps of the process and thus eliminate the attendantoperating difficulties.

A further object of the invention is to eliminate the necessity ofpurification of the halogencontainin liquor obtained by leaching theadsorbent agent.

A further object of the invention is to permit the use of a smalleramount of water than heretofore required for leaching the halogen saltsor 5 compounds from the adsorbent agent and thus obtain a moreconcentrated halogen-containing liquor. In this manner, the evaporationof water from the liquor, for the purpose of concentration, prior to therecovery of the halogen therefrom, may be partly or entirely eliminated.

A further object of the invention is to obtain a leached liquorsubstantially free of impurities, which may be more advantageouslytreated for the recovery of halogen, either by precipitation orsublimation. In case chemical treatment is used as a means of effectingprecipitation or recovery of the halogen from such liquor, the amount ofchemicals required for such treatment is thus materially reduced.Furthermore, the halogen product obtained, by precipitation,sublimation, distillation, or other suitable treatment, is of higherpurity.

A further object of the invention is to obtain a higher yield ofhalogen, due to more complete 25 removal of the halogen salts orcompounds from the adsorbent agent in the leaching operation and to amore complete recovery of the halogen from the leached liquor byprecipitation or sublimation.

A further increase in yield is obtained. due to the fact that thepurification method of the present invention leads to the recovery ofhalogen contained in organic halogen compounds adsorbed in the adsorbentagent, and furthermore, eliminates the tendency to form additionalorganic halides upon acidification of the leached liquor prior toprecipitation or sublimation. The formation of organic halogen compoundsat this stage of the process is prevented by the elimination of organicimpurities prior to the leaching operation.

In the recovery of iodine, the fact that the iodine product obtained byprecipitation or sublimation from the leached liquor is of higher purityalso results in a further increase in final yield, due to the factthatthe time required for drying the iodine crystals is materially reduced,which results in a corresponding reduction in the loss of iodine due tovolatilization during the drying operation.

A further object of the invention is to reactivate or improve theadsorbent properties of the adsorbent agent remaining after leaching ofthe halogen salts or compounds therefrom. Since economical operation ofa process of the type above described demands that the adsorbent berepeatedly re-used for adsorption of halogen from further quantities ofbrine or solution, it will be obvious that the improvement in theadsorbent properties of the recovered adsorbent agent thus elfected willenable a higher recovery of halogen by adsorption in the re-used agent,or a reduction in the amount of such agent required. Furthermore, thesettling of the adsorbent from the brine or solution, following theadsorption step. is rendered more rapid and complete, due to theimprovement in physical properties thereof.

In the process of the present invention, the elimination of organic orvolatile impurities is effected by heating the adsorbent mass, followingthe adsorption of halogen therein and the chemical treatment forconversion of the halogen to substantially non-volatile salts or othercompounds, to a sufiicient temperature to eliminate organic impurities,together with any other volatile impurities which may be present.

The chemical treatment to which the adsorbed halogen is subjected, priorto the heating operation for removal of organic impurities, consists intreatment with a reagent adapted to react with elemental halogen to forma substantially nonvolatile compound or substance, that is, a substanceWhich is substantially non-volatile the temperature employed in saidheating operation; according to a preferred embodiment of the process,the chemical treatment serves to convert the halogen to a Water-solublecompound or compounds, so that the recovery thereof from the adsorbent,following the heating operation, may be effected by a water-washing orleaching of the adsorbent mass.

When charcoal is used as the adsorbent agent, heating of the adsorbentmass is preferably con ducted in an enclosed chamber, by application ofindirect heat, with the substantial exclusion of oxygen, wherebyoxidation of the charcoal itself is prevented. The character of theheating is such that a decomposition or destructive distillation of theorganic impurities is obtained, without dissociation or volatilizationof the halogen salts or compounds, Impurities of an oily nature, as wellas other organic impurities present in the charcoal mass, are eliminatedby such heat treatment, either by volatilization, or by conversionthereof into coke or other solid carbonaceous residuum in substantiallyinsoluble state deposited on the charcoal. It has been found practicalto heat the charcoal mass to a temperature of from between 400 and 500F., which produces substantially complete elimination of organicimpurities, without loss of halogen by decomposition or volatilizationof the halogen salts or compounds.

If desired, the heating may be conducted under super-atmospheric orsubatmospheric pressure conditions. but it has been found quitepractical to conduct the heating at ordinary atmospheric pressures. Thevolatile organic constituents of the charcoal mass, removed by heating,may be recovered, if desired, by condensation, absorption, chemicaltreatment or in any other suitable manner.

In the treatment of oil-field brines by charcoal adsorption methods, aconsiderable amount of organic matter is picked up by the adsorbentcharcoal and while some of the halogen may be present in the charcoal incombination with organic matter, the treatment used for conversion ofthe halogen to non-volatile salts will, in general, cause the principalproportion of such halogen to be taken out of combination with theorganic matter, but the organic matter itself remains, and the presentdisclosed treatment of the charcoal mass after the chemical conversionof the adsorbed elemental halogen serves to remove the organic matterbodily, or at least convert it into a state which does not interferewith the halogen recovery in the subsequent steps of the process.

After the heat treatment is completed, and the organic impuritiessubstantially completely eliminated, the remaining charcoal mass issubjected to further treatment for the recovery of thehalogen-containing compound or substance therefrom. For example, if thehalogen has been con vcrted into a water-soluble substance, it may berecovered by washing or leaching with water.

As an example of the application of the present invention to thecommercial recovery of iodine from oilfield brines, the brine is firsttreatcd to convert any combined iodine into elemental iodine, forexample, by acidification and oxidation in any well-known manner, andadsorbent charcoal is then added for the purpose of taking up theiodine. This charcoal is separated from the brine by settling orfiltration, and is then treated with a reagent capable of reacting withthe iodine to form a substantially non-volatile substance. for example,with an aqueous solution of an alkali, such as caustic soda, causticpotash, or alkali-metal carbonate. Hitherto it has been customary todigest the charcoal with the alkaline solution and then subject the massto filtration and Washing with water to extract the soluble iodine saltsfrom the charcoal. This procedure succeeds in converting the iodine intothe desired water-soluble salts, but a considerable amount of organicmatter is also caused to enter the water, either in solution or insuspension, and is thus caused to be present during the subsequent stepsfor recovery of the iodine in commercially marketable form. According toa preferred embodiment of the present invention, however, theiodine-containing charcoal is treated with an aqueous alkaline solutiontioned, preferably in slight excess over the amount theoreticallyrequired for conve'sion of the iodine, and is then subjected to theheating operation above-described. This may advantageously beaccomplished by coal into a slurry with the alkaline solution, and thenevaporating the moisture from the slurry, after which the mass may beheated to a tern-- perature of approximately 450 F., as an example.

in an enclosed chamber with exclusion of oxygen, and the organic mattereliminated. Due to the fact that the charcoal is treated with alkali inthis manner, only a slight excess of the theoretical. amount of suchalkali is required for the conversion reaction, and thus there isimportant economy in consumption of reagents obtained in this particularstep. The reason for the fact that a smaller excess of the alkalinereagent is required for conversion of the elenzental iodine to a salt,is that as the slurry is evapo rated to dryness a concentration ofunreacted alkaline solution is continually obtained, and thus theconversion reaction can progress to th desired end without requiringthat a amount of reagent be kept in solution.

Any suitable form of apparatus may be em ployed for the heatingoperation, but I prefer to use an aparatus which provides forevaporation of the slurry to dryness under conditions of agitation, andwhich is adapted for proper such as above-men making the char largeheating of the dried mass to the desired temporature while providing forsuitable heattransfer through the mass for uniform heating. Theapparatus should provide for the substantial exclusion of oxygen duringthe heating operation when charcoal is employed as the adsorbent agent,and should preferably also provide for agitation of the mass to preventcaking and occlusion of volatilized impurities.

After the heating operation, the charcoal, which now containssubstantially only the iodine salts and that portion of the organicmatter which has been converted to coke or the like, is subjected to aWater leaching operation. It has been found that only about one-half thehitherto-required amount of water is necessary for this leachingoperation, which effects a further economy in op eration in view of thefact that it has been hither to cons dered preferable to evaporate theliquor obtained by leaching, to obtain a concentration of the saltstherein before proceeding further with the process. It is believed thatthe leaching operation requires less water than has been hithertoconsidered necessary for the reason that substantially no organic matteris present in the charcoal mass. It has been noted that considerablymore water than a theoretical consideration would call for has beenhitherto necessary for leaching of the charcoal mass, and the logicalassumption is that the organic matter present has acted to mechanicallyinterfere with the leaching action. The fact that only a slight excessof the alkaline reagents remain in the charcoal mass after the heatingoperation according to the present invention, may also contribute to theease of leaching.

The leached charcoal is used for further adsorption of iodine from thebrines, and it has been found that this charcoal is materially moreadsorptive than charcoal which has been leached as above describedwithout removal of the organic matter by heating. This appears quitelogical in View of the fact that any organic matter present in thecharcoal will necessarily seriously interfere with subsequent adsorptionand will diminsh the adsorptve power thereof, and removal of the organicmatter from the charcoal in the present described manner acts torevivify the charcoal and thus enable the same to take on furtherquantities of iodine. It has been found that charcoal recovered in themanner herein set forth may be re-used a materially greater number oftimes before becoming worthless for adsorption use, than has beenhitherto possible. This feature of the present process adds stillanother economy in operation.

The liquor obtained by leaching the heated charcoal is then treated withacid or the like, preferably in the presence of a suitable oxidizingagent such as potassium dichromate or chlorine, and the iodine convertedinto free state. If desired, the liquor may be concentrated byevaporation before the oxidation step, but in general this is notnecessary in the present process due to the reduced amount of water usedin the leaching operation. As above pointed out, it has been hithertoconsidered preferable to concentrate this liquor, but the presentprocess provides for obtaining a liquor of the desired concentrationdirectly, without such concentration procedure. The absence of organicmatter in the liquor enables a lesser amount of oxidizing agent to beused, and the fact that only a slight excess of alkali is present enables a lesser amount of acid to be used in obtaining the desiredacid-concentration for liberation of the iodine. Thus, further economiesin the process are realzed, due to a lowered consumption of reagents.

It is customary to recover the freed iodine from the liquor byfiltration, or by direct sublimation, and inasmuch as the iodine isproduced in a substantally organic-free state, it is of relatively highpurity. and the time required for drying of the resulting iodinecrystals is materially lowered, which obtains a lower iodine loss inthis portion of the recovery process.

It will be apparent that the process of the present invention is notlimited to the use of a reagent which will convert the adsorbed iodineor other halogen into a water-soluble material prior to the heatingoperation, as set forth in the above specific embodiment, but is equallyadaptable when an agent such as silver nitrate is used to convert thehalogen into a water-insoluble, non-volatile substance, such as a silverhalide, from which the halogen may be recovered by subjecting theabsorbent mass to suitable chemical treatment and leaching according toknown methods, subsequent to the heating operation.

While the specific embodiment of the present invention is directed tothe recovery of iodine from oil-field brines, it will be apparent thatthis invention is applicable to the recovery of other halogens such asfor example, bromine, from any brine or liquor which is contaminatedwith organic matter.

I claim:

3. The process for recovery of halogens from solutions containing thesame which comprises: adsorbing elemental halogen on an adsorbent agent;contacting said adsorbent agent containing adsorbed halogen with anaqueous solution of a reagent capable of reacting with said halogen toform a substantially non-volatile substance, so as to produce a wetmixture containing said adsorbent agent and said substance; heating saidmixture to dry the same and el minate organic impurities therefrom whileretaining said adsorbent agent and said substance in the dried mixture;separating said substance from said adsorbent agent: converting thehalogen contained in said substance to elemental form; and recoveringsaid halogen.

2. The process of recovering a halogen from a solution containing thesame which comprises: converting the halogen into elemental form;adsorbing elemental halogen on charcoal; contacting said charcoalcontaining adsorbed halogen with an aqueous solution of a reagentcapable of reacting with said halogen to form a substantiallynon-volatile substance, so as to produce a wet mixture containing saidcharcoal and said substance; heating said mixture to dry the same andeliminate organic impurities therefrom while retaining said charcoal andsaid substance in the dried mixture: converting the halogen contained insaid substance to elemental form; and recovering said halogen.

3. The process of recovering iodine from solu tions containing the samewhich comprises: converting the iodine to elemental form; adsorbing saidiodine on charcoal; contacting said charcoal containing adsorbed iodinewith an aqueous solution of a reagent capable of reacting with saidiodine to form a substantially non-volatile substance. so as to producea wet mixture containing said charcoal and said substance; heating saidmixture to dry the same and eliminate organic impurities therefrom whileretaining said charcoal and said substance in the dried mixture;

separating said substance from said charcoal; converting the iodinecontained in said substance to elemental iodine; and recovering saidiodine.

4. In a process for recovery of halogens from solutions containing thesame, the steps which comprise: adsorbing elemental halogen on anadsorbent agent; contacting said adsorbent agent containing adsorbedhalogen with an aqueous solution of a reagent capable of reacting withsaid halogen to form a water-soluble salt thereof, to produce a wetmixture containing said adsorbent agent and said salt; heating saidmixture to dry the same and eliminate organic impurities therefrom whileretaining said adsorbent agent and said salt in the dried mixture;leaching said salt from said adsorbent agent; converting the halogencontained in said salt to elemental form; and recovering said halogen.

5. In a process for recovery of a halogen from a solution containing thesame, the steps which comprise: adsorbing elemental halogen on charcoal;contacting said charcoal containing adsorbed halogen with an aqueoussolution of a reagent capable of reacting with said halogen to form awater-soluble salt thereof, so as to produce a wet mixture containingsaid charcoal and said salt; heating said mixture in the substantialabsence of oxygen to eliminate organic impurities therefrom Whileretaining said charcoal and said salt in the dried mixture; leachingsaid salt from said charcoal; converting the halogen in said salt toelemental form; and recovering said halogen.

6. in a process for recovering iodine from a solution containing thesame, the steps which comprise: adsorbing elemental iodine on charcoal;contacting said charcoal containing adsorbed iodine with an aqueoussolution capable of reacting with said iodine to form a water solublesalt thereof, so as to produce a Wet mixture containing said charcoaland said salt; heating said mixture in the substantial absence of oxygento dry the same and eliminate organic impurities therefrom whileretaining said charcoal and said salt in the dried mixture; leachingsaid salt from said charcoal; converting the iodine in said salt toelemental form; and recovering said iodine.

7. In a process for recovery of halogen from a solution containing thesame, the steps which comprise: adsorbing elemental halogen on anadsorbent agent; contacting said adsorbent agent containing adsorbedhalogen with an aqueous solution of a reagent capable of reacting withsaid halogen to form a water-soluble salt, so as to produce a wetmixture containing said adsorbent agent and said salt; and heating saidmixture to dry the same and eliminate organic impurities therefrom whileretaining said adsorbent agent and said salt in the dried mixture.

8. In a process for recovery of a halogen from a solution containing thesame, the steps which comprise: adsorbing elemental halogen on charcoal;contacting said charcoal containing adsorbed halogen with an aqueoussolution of a re agent capable of reacting with said halogen to form awater-soluble salt thereof, so as to produce a wet mixture containingsaid charcoal and said salt; and heating said mixture in the substantialabsence of oxygen to dry the same and eliminate organic impuritiestherefrom, while retaining said charcoal and said salt in the driedmixture.

9. In a process for recovery of iodine from a solution containing thesame. the steps which comprise: adsorbing elemental iodine on charcoal;contacting said charcoal containing adsorbed iodine with an aqueoussolution of a reagent capable of reacting with said iodine to form awater-soluble salt thereof, so as to produce a wet mixture containingsaid charcoal and said salt; and heating said mixture in the substantialabsence of oxygen to dry the same and eliminate organic impuritiestherefrom, while retaining said charcoal and said salt in the driedmixture.

10. The invention set forth in claim 9, said mixture being heated to atemperature between 400 and 500 F.

11. In a process for recovery of iodine, the step which comprises:heating a wet mixture containing an adsorbent agent and a Water-solublesalt of iodine, to dry said mixture and remove organic impuritiestherefrom, while retaining said adsorbent agent and said iodine salt inthe dried mixture,

12. In a process for recovery of iodine, the step which comprises:heating a wet mixture containing charcoal and a Water-soluble salt ofiodine to a temperature between 400 and 500 F. in the substantialabsence of oxygen, to dry said mixture and eliminate organic impuritiestherefrom.

13. In a process for recovery of a halogen from solutions containing thesame, the steps which comprise: adsorbing elemental halogen on anadsorbent agent; treating said adsorbent agent with an aqueous solutionof an alkaline material in slight excess over the theoretical amountrequired for conversion of said halogen into water-soluble saltsthereof, and forming a slurry; reducing said slurry to a dry mass;heating said mass to eliminate organic impurities therefrom; leachingsaid mass with water to separate said water-soluble salts from saidadsorbent agent; and recovering the halogen from said Watersolublesalts.

14. The invention set forth in claim 13 and comprising in addition:re-using said adsorbent agent obtained by said leaching in theadsorption of further quantities of halogen.

15. In a process for recovering iodine from solutions containing thesame, the steps which comprise: adsorbing elemental iodine on charcoal;treating said charcoal in slight excess with an alkaline reagent toconvert said iodine into water-soluble salts and form a slurry; reducingsaid slurry to a dry mass; heating said mass in the substantial absenceof oxygen to eliminate organic impurities therefrom; separating saidsalts from said charcoal by leaching with water; and converting theiodine contained in said salts to elemental iodine.

16. The invention set forth in claim 15, and comprising in addition:re-using the charcoal separated from said water-soluble salts by saidleaching for the adsorption of further quantities of elemental iodine.

1'7. In a process for recovering a halogen from a solution containingthe same, the steps which comprise: adsorbing elemental halogen on anadsorbent agent; contacting said adsorbent agent containing adsorbedhalogen with an aqueous solution of a reagent capable of reacting withsaid halogen to form a substantially non-volatile substance, so as toproduce a wet mixture containing said adsorbent agent and saidsubstance; heating said mixture to dry the same and to eliminate organicimpurities therefrom, while retaining said adsorbent agent and saidsubstance in the dried mixture; and recovering said halogen in elementalform.

18. In a process for recovering iodine from a solution containing thesame, the steps which comprise: adsorbing elemental iodine on charcoal;contacting said charcoal containing adsorbed iodine with an aqueoussolution Capable of reacting with said iodine to form a substantiallynon-volatile substance, so as to produce a wet mixture containing saidadsorbent agent and said substance; heating said mixture in thesubstantial absence of oxygen, to dry said mixture and eliminate organicimpurities therefrom, while retaining said charcoal and said substancein the dried mixture; and recovering said iodine in elemental form.

19. In a process for recovery of iodine, the step which comprises:heating a wet mixture containing an adsorbent agent and a substantiallynonvolatile iodine-containing substance, to dry said mixture and removeorganic impurities therefrom, while retaining said adsorbent agent andsaid iodine-containing substance in the dried mixture.

20. In a process for recovering iodine, the step which comprises:heating a wet mixture containing charcoal and a substantiallynon-volatile iodine-containing substance, to a temperature between 400and 500 F. in the substantial absence of oxygen, to dry said mixture andeliminate organic impurities therefrom.

HARRY E. BIERBAUM.

